VB - Arithmetic In ASCII

I'm trying to design an encryption program in which the text is converted into its ASCII Code Equivalent and then uses math to change the text and then convert the result into its ASCII Char. I have managed to convert the string I wish to encrypt into its ASCII Code but when it comes to doing the math for the next task I receive syntax errors. Where the exclamation is in the code below is where the code I'm having trouble is. Thanks in advance....

For Counter = 0 To UBound(CharArray)
CipherText = CipherText & Asc(CharArray(Counter)) + 94
! Here I want to use an IF Statement to check if any of the ASCII Code exceed 126 and if so, subtract 37
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